Cobalt

Cobalt, chemical element, symbol Co; for physical constants see Periodic Table. Cobalt was discovered by Georg Brandt in 1735. Cobalt is a gray-white, lustrous, hard and brittle magnetic metal. It is alloyed with other elements to make powerful magnets and high speed cutting tools. Compounds of cobalt have been used for centuries to give a blue color to ceramic materials. Radioactive cobalt-60, an artificial isotope, is a powerful source of gamma rays and is used in the treatment of cancer.